Template-Free Fabrication of Single Atom Fe-Based Cathodes Unlock High-Performing Anion-Exchange Membrane Fuel Cells

Single-atom catalysts (SACs) possessing well-defined active sites of singular metal atoms have gained prominence in the field of electrocatalysis as they can be tuned to enhance activity and stability. In this study, a critical-raw-material (CRM)-free SAC is synthesized for the oxygen reduction reaction (ORR) in alkaline media by pyrolyzing polyimide nanoparticles and Fe without using a sacrificial template. Upon purification, the resulting catalyst demonstrates outstanding performance as cathodes in anion-exchange membrane fuel cells (AEMFCs) owing to sufficiently stabilized Fe single-atoms at the FeN₄ sites yielding a peak power density (P_max) as high as ∼1.8 W cm^-2 and specific power values up to 11.3 W ${\mathrm{mg}}_{\mathrm{PGM}}^{-1}$ ; the latter being the greatest reported among CRM-free cathode AEMFCs. The SAC also shows remarkable in situ durability under a very high current density of 1000 mA cm^-2, a first introduced here, with only a 2 mV h^-1 decay. Most impressively, when the SAC is combined with a NiMo anode to test a completely CRM-free high-temperature (HT)-AEMFC at 118 °C, a P_max of 372 mW cm^-2 and limiting current density of ∼1.14 A cm^-2 are achieved. This work represents a significant milestone in the development of durable SAC cathode catalysts for the next generation of CRM-free AEMFCs.